1. Field of the Invention
The present invention generally relates to the field of motion-sensed activation of an electrical lamp, and in particular, it relates to an integrated assembly of motion-sensing electronics, optics, and an electrical lamp fixture that is adapted for installation in a recess or a cavity in ceilings or on walls.
2. Description of the Related Art
Activation of electrical lamp based on the detection of human motion is commonly used as a security arrangement. In a large number of installations, this arrangement is also used to conserve electricity. In both applications, electrical lamp remains turned off until light needs to be turned on for humans approaching an area covered by a motion detector, which, upon sensing human-source infrared radiation, releases electrical current to the lamp. Electrical power remains available to the lighting fixture at all times, but it is the motion and ambient light sensors and associated logic circuits which determine if and when to turn the lights on.
Lights that are activated by motion detector(s) generally include a pair of passive infrared sensors disposed within the motion detector's housing. PIR sensors detect infrared radiation emitted by objects that generate heat, including humans who emit infrared radiation that is strongest at a wavelength of 9.4 micrometer. To respond only to the movement of humans, all wavelengths outside of the band of interest, typically the 8–14 micrometer band, are electronically filtered out. A typical motion detector responds to the movement of humans by generating a small electrical charge that is further conditioned to switch on electrical current to a lamp(s) within the electrical light assembly that is to be activated by the motion detector. Motion detectors generally consist of a pair of motion sensors made of pyro-electric material. A focusing device is also installed within the motion detector subassembly to focus incoming IR radiation to one or the other sensor in the PIR sensor pair. The most commonly used focusing device is a Fresnel lens, though other devices such as a shadow lens consisting of baffle strips are also in common use. PIR, IR and focusing devices including Fresnel lens are widely covered in various disclosures, such as U.S. Pat. No. 4,258,255 for PIR devices and U.S. Pat. No. 2,736,894, RE035,534 and others for Fresnel lens type of focusing devices.
Decorative and security lamps with integral or electro-mechanically attached motion sensors are relatively well known in the art. Examples of such lamps are disclosed in U.S. Pat. Nos. 4,982,176 and 5,282,118. Decorative lamps come in a variety of designs: there are security lights in which the electrical lamp(s) and PIR motion sensor assembly are physically detached but electrically connected; also available are fully integrated units such as a coach lantern design disclosed in U.S. Pat. No. 5,626,417. Virtually all such units in current use have logic circuits within the lamp assembly, which logic circuits determine when electrical current needs to be applied to the electrical lamp contained within the assembly. That determination derives from such inputs as ambient light and the intensity and rate of change in infrared energy.
In certain installations where a plurality of electrical lamps needs to be operated in a single electrical wiring circuit, each lamp may be fitted with its own motion sensor. Alternately, a single motion sensor may be configured to power up the entire electrical circuit that in turn powers up all lamps in the circuit.
A problem arises when a recessed light assembly is to be installed in conjunction with a motion detector. Currently available recessed light assemblies require that the motion detector subassembly be installed separately with significant effort while the end result is aesthetically unpleasant. The issue remains unchanged even when a single electrical switch controls power to a recessed light assembly and to a non-recessed lamp with an integrated motion detector subassembly. This type of circuitry is common in many North American homes where a single electrical switch controls electric power to decorative lantern(s) installed at curbside or near garage door, as well as to recess light(s) installed in a patio at front entrance. The problem with such combination lighting circuits is that they power up only when the motion sensor in the decorative lighting fixture detects motion, but not when humans approach the recessed light, such as when exiting the home from the front entrance. This disadvantage renders such installations partly or completely ineffective. It is possible to equip the recessed light(s) with a standard standalone motion detector; however, that would be aesthetically unpleasant. Thus, it is evident that the recessed light must have its own motion detector for the entire circuit to function properly.
Along with the aesthetics aspect noted above, installation of a standalone motion sensor with a recessed lighting fixture is cumbersome and expensive, as it requires cutting into wood, stucco, and/or brick construction materials to lay down wiring and to install the additional motion detector subassembly.
Yet another problem with the use of a standalone motion sensor is the design of the Fresnel lens that is more suited for a motion detector subassembly which stands out, or sticks out, from the mounting surface. Such a configuration is not best suited for a recessed light since recessed lights are generally installed in ceilings.
In view of the issues cited above, there exists a need for a recessed light assembly integrated with a motion detector in an aesthetically pleasant and functionally correct housing.